This invention relates generally to a device and method used in the manufacture of composite optical lenses, and more particularly to a device and method for spreading liquid bonding material evenly between the individual lens wafers used in making a composite optical lens, such as a lens for eyeglasses.
Optical lenses have a front outer surface and a back outer surface, through each of which light enters and leaves the lens. A composite lens is made by joining together a separately-formed front lens wafer and a separately-formed back lens wafer. Each lens wafer has an outer surface and a bonding surface. The wafers are joined together at their bonding surfaces. The outer surfaces of the front and back wafers form, respectively, the front outer surface and back outer surface of the composite lens.
When a composite lens is to be used for eyeglasses, the front lens wafer has a convex outer surface and a concave bonding surface. The back lens wafer has a concave outer surface and a convex bonding surface that matches the concave bonding surface of the front wafer. The two wafers are joined together by spreading a liquid bonding material evenly across the bonding surfaces of the wafers and assembling the wafers so their bonding surfaces are brought together. The bonding material is subsequently cured.
One problem in the manufacture of composite lenses is in preventing bubbles of air from being trapped in the bonding material between the lens wafers. For composite lenses made from glass wafers, such air bubbles can be forced out from between the wafers by applying finger pressure at a number of points to the outer surfaces of the assembled wafers before the bonding material is cured.
However, for composite lenses made from thin plastic lens wafers, the application of finger pressure can cause deformation of the wafers at each specific point where the pressure is applied. These deformations in turn cause the layer of bonding material to become uneven. This can cause optical distortions in the composite lens.